瞬时频率引导的小波变换轮廓术相位解包裹技术

提出了一种新的用于小波变换轮廓术进行相位解 包裹的质量图建立方法。对受物体形貌调制的变形 条纹图,利用小波变换相位解调技术获得变形条纹的包裹相位与瞬时频率；将瞬时频率与条 纹载频的绝对 差值和相邻像素点之间瞬时频率的变化程度两方面建立质量图,质量图值的大小可表示位 相质量的好坏, 质量图的值越小,相位质量越可靠；再设定阈值,将质量图分为质量好坏两部分,不同 部分分别采用 扫描线算法和洪流相位解包裹法进行位相解包裹。本文方法在提高解包裹处理速度的同时, 还可以更为精确 地检测出噪声、阴影或条纹突变等区域,使相位解包裹精度和效率得到了保证。通过理论分 析、仿真分析、 实物静态和动态实验表明,与现有的质量图引导的洪流相位解包裹法 相比,本文方法解包裹速 度更快,适用于动态测量中大量变形条纹图的相位精确快速解包裹。

Phase unwrapping guided by instantaneous frequency for wavelet transform profilometry

A novel quality map algorithm for wavelet transform profilometry is pr esented to improve the accuracy and efficiency of the phase unwrapping.1-D wavelet transform is first ly applied to the deformed fringe pattern to derive the wrapped phase and the instantaneous frequency.The quality map as the guidance for phase unwrapping is then established with two factors.The one is the absolute differe nce between the instantaneous frequency and the fringe carrier frequency.The other is the change of instantan eous frequency over adjacent pixels.The value of the quality map determines the quality of the wrapped phase. The smaller the value,the higher reliability of the wrapped phase.Then the quality map is divided into tw o parts by the pre-set threshold. The scan-line algorithm is used to unwrap the phase within the low-quality ar eas while the flood-fill algorithm is used within the high-quality areas.The proposed method is verified by static experiments a nd dynamic experiments.The quality map can precisely indicate the areas where noise,shadows or fringe abru pt changes exist.Our experiments demonstrate that the proposed algorithm outperforms the flood-fill phase unwrapping algorithm in terms of accuracy and computational time.The proposed algorithm is suitable for dynamic measurement where a large number of fringe patterns require accurate phase unwrapping.